Study on the Resonant Behaviors of a Bottom-Hinged Oscillating Wave Surge Converter

This paper studied the resonant behaviors of a bottom-hinged oscillating wave surge converter (OWSC) as well as the relationship of resonance with the response and capture width ratio (CWR). The time-domain dynamic equation of an OWSC in shallow water based on the boundary element method (BEM) was solved by a Python code, considering the corrected wave surface and the nonlinearities of restoring moment, drag, and friction. The unknown factors, such as wave surface corrected factor and drag coefficient, were effectively calibrated with computational fluid dynamics (CFD) method. An intermediate initial angle in free decay is appropriate for use to determine the natural period. Under regular waves, the resonance occurs near the natural period for the uniform wave amplitude, rather than the uniform wave torque amplitude, and can disappear due to the amplification of Power Take-Off (PTO) friction. Under unit-amplitude regular waves, the period of maximum CWR is relatively close to the period of maximum velocity, but far from the resonant period. Under irregular waves, no stable resonance is observed because the maximum equivalent pitch angle appears at different peak periods of wave spectra with the variation in PTO damping. When the period of a regular wave or the peak period of an irregular wave is close to the natural period, a phase hysteresis of velocity relative to wave torque always occurs.

Generic Upscaling Methodology of a Floating Offshore Wind Turbine

This study presents a generic method to upscale a semi-submersible substructure and tower-nacelle-blade for a floating offshore wind turbine from 5 MW to 15 MW and beyond. The effects of upscaling the column radius and/or distance of the floating base are investigated, and a comparison is made with a 15 MW reference design. It is found that scaling column radius increases the mass of the platform and the heave natural period, while scaling column distance raises the center of gravity and metacentric height of the floating system and slightly decreases the heave natural period. The 15 MW reference design addresses these issues through design changes that increase the ballast mass to lower the center of gravity, and increase the added mass to raise the heave natural period. Finally, a method for estimating the scaling of platform parameters with different assumptions is proposed.

Developing Earthquake-Resistant Structural Design Standard for Malaysia Based on Eurocode 8: Challenges and Recommendations

In late 2017, the Malaysian National Annex (NA) to Eurocode 8 (EC8) was released and enacted following some 13 years of deliberations and preparations. The authors of this paper aim to use this article to share their experiences and reflections during this period of developing the first national standard for the seismic design of buildings for Malaysia. To begin with, there were major challenges in implementing the 20-year-old EC8 framework for a country so far away from Europe. The first challenge was adapting the probabilistic seismic hazard assessment (PSHA) methodology in a low-to-moderate seismicity region where the paucity of representative seismic data presented a great deal of uncertainties. To address this situation, imposing a minimum level of seismic hazard was recommended. The second challenge was about dealing with the outdated EC8 site classification scheme, which poorly represents the potential effects of soil amplification in certain geological settings. To address this situation, an alternative site classification scheme in which the site natural period is an explicit modelling parameter was introduced. The third challenge was concerned with difficulties generated by the EC8 provisions mandating Ductility Class Medium (DCM) detailing in certain localities where the level of seismic hazard is predicted to exceed a certain threshold. To address this situation, the viable option of using strength to trade off for ductility was recommended, or in cases where ductility design is needed, a simplified set of code-compliant DCM designs was presented. The fourth challenge was about handling the requirements of EC8 that the majority of buildings are to involve dynamic analysis in their structural design when the majority of practising professionals did not have the skills of exercising proper use of the requisite software. To address this situation, a generalized force method was introduced to control the use dynamic analysis in commercial software. It is hoped that, through sharing the lessons learnt, code drafters for the future would be able to find ways of circumventing the multitude of challenges with clear thinking and pragmatism.

Experimental Verification of Analysis Model of Seismic Isolation With High-Static-Low-Dynamic Stiffness

This paper verifies the model of high-static-low-dynamic stiffness (HSLDS) for seismic isolation based on an experiment. Seismic isolation is widely used in several countries. Moreover, the number of seismically isolated buildings has rapidly increased in these few decades. Seismic isolation extends a natural period of a building and decreases the absolute acceleration to re-duce a seismic force. However, as there is a trade-off between displacement and absolute acceleration, it might result in the maximum displacement be-yond an allowable range. HSLDS is nonlinear, and its restoring force can be approximated cube of a displacement. Thus, HSLDS applies a large restoring force for significant displacement, and the force is small for small perturbation around an equilibrium position. To improve the control performance of seismic isolation for displacement, we apply HSLDS for seismic isolation. This paper conducts an experiment and compares the results with a time-history analysis to verify a numerical model of HSLDS

Evaluating the Vertical Extension Module of a Building with Installed Rotary Dampers at Joints

In this study, the shape of a vertical expansion module with a rotary-type damping device is proposed. The external energy dissipation capacity is confirmed through experiments and the performance of the module is simulated. It can be easily applied to high-rise structures, as the module is directly supported by the bearing walls without the need for a separate base system. Additionally, as the damper can be replaced, it is possible to enhance seismic performance even after construction. The simulation results show that the rotary-type damper is more effective in reducing the displacement, shear force, and moment than free and fixed joints. In the pushover analysis of a system modeled using the moment hinge of the rotary damper of the joint, the best response reduction effect is obtained when the yield moment of the hinge is defined as 1% of the frame plastic moment. As a result of the analysis of the multi-degree-of-freedom system considering a harmonic load, we determined that it is efficient for the hinge to yield after the displacement, and the acceleration response of the resonant structure reaches steady state during the installation. In the multi-degree-of-freedom system with slab joints added to the analytical model, the displacement response decreased gradually as the natural period of the structure decreased and the joint increased. This provides evidence that the damper does not affect the overall behavior of the structure. The most important design factor of the rotary-type friction damper, shown through the experiment, is the relationship between the frictional surface and the tightening force of the bolt.

Laboratory Study of Integrated Wet-Towing of a Triple-Bucket Jacket Foundation for Far-Offshore Applications

As a form of clean and low-carbon green energy, offshore wind power occupies an important position in the global energy structure. With the rapid development of the wind power industry, wind power projects gradually develop from offshore to far-offshore sea areas. The multi-bucket jacket foundation is a considerable foundation type for far off-shore projects, but high installation costs involving ship transportation with parted components and field installation has significantly hindered its wide application. In this study, based on a 6.7-MW triple-bucket jacket foundation (TBJF) project of a deep-sea wind farm in China, a new integrated wet-towing method of “jacket + triple-bucket foundation” composite structure was proposed, which is suitable for far long-distance transportation of far-offshore applications. The static-model test of both self-stability and wet-towing stability was conducted. Based on the test and the numerical results, the natural period of the foundation for different draft depths in hydrostatic water and the stability for different eccentric loads were first evaluated. Then, the effects of different wet-towing modes and sea conditions on the stability of the TBJF were investigated. Finally, the optimal wet-towing mode and applicable sea conditions for the TBJF structure were proposed.

Changes in and Modelling of Hydrological Process for a Semi-Arid Catchment in the Context of Human Disturbance

Hydrological modelling is of critical importance to flood control. However, flood forecasting in semi-arid region is a great challenge to hydrologists, particularly in a changing environment. Taking the Zhulong River catchment located in north China as a case, the performance of GR4J model for hydrological modelling was investigated based on the analysis for changes in hydrological process of three periods defined as natural period (1967–1979), moderate human impact period (1980–1996) and intensive human impact period (1997–2015). Results show that 1) the annual precipitation and temperature of the catchment both presented upward trends, while the annual observed runoff exhibited a significant downward trend in the time span from 1967 to 2015; 2) the correlations between runoff and precipitation were comparatively higher on both monthly and annual scales in natural period than those in human disturbed periods; 3) both annual runoff and daily peak discharge in human disturbed periods decreased relative to those in natural period due to the environmental changes; 4) the GR4J model performed well for runoff simulations in natural period but gradually lost its applicability with the intensification of human activities. It is essential to improve the accuracy of hydrological modelling under a changing environment in further studies.

THE BODY MASS INDEX (BMI) RELATED TO MENOPAUSE SYMPTOMS

Background : Menopause is a natural period in a woman's life related to hormonal changes and is marked by the cessation of menstruation in the last 12 months and can cause a wide range of sometimes bothersome menopause symptoms. That menopause symptoms associated with several risk factors such as Body Mass Index (BMI) and knowledge. The study aims to identify the relationship of BMI and knowledge with menopause symptoms in the Shafa group Padang Petok Nagari Panti Selatan. Method : This research is analitic observational research with cross sectional approach. The sampling technique was carried out by total sampling consisting of 55 respondents with inclusion criteria menopause women aged 45-65 years who have not experienced dementia, have good awareness and willing to be respondents. Data were obtained by weighing, measuring height and filling out The Menopause Rating Scale to evaluate the severity of menopause-related symptoms by respondents. Afterwards the data was analyzed by the Spearman rho test to see the association between BMI and knowledge with menopause symptoms. Result : The research shows 65,4% respondents with high BMI, 72,7% with lacking of knowledge and 60% with severe menopause symptoms. The results of the Spearman rho test showed a relationship between BMI and menopause symptoms (p value = 0.000), but there is no relationship between knowledge of menopause and menopause symptoms (p= 0,450). Conclusion : BMI related to menopause symptoms. Menopause women must monitor their weight in an effort to prevent these complaints.

Comparative Study, Design and Analysis of a G+12 Structure in Earthquake Zone in India

Seismic isolation is a technology that decouples a building structure from the damaging earthquake motion. It is a simple structural design approach to mitigate or reduce potential earthquake damage. In base-isolated structures, the seismic protection is obtained by shifting the natural period of the structure away from the range of the frequencies for which the maximum amplification effects of the ground motion are expected; thus, the seismic input energy is significantly reduced. At the same time, the reduction of the high deformations attained at the base of the structure is possible, thanks to the energy dissipation caused by the damping and the hysteretic properties of these devices, further improving the reduction of responses of the structures. Base isolation is also an attractive retrofitting strategy to improve the seismic performance of existing bridges and monumental historic building.  The method of base isolation was developed in an attempt to mitigate the effects of earthquakes on buildings during earthquakes and has been practically proven to be the one of the very effective methods in the past several decades.  Base isolation consists of the installation of support mechanism which decouples the structure from earthquake induced ground motions.  Base isolation allows to filter the input forcing functions and to avoid acceleration seismic forces on the structure.  If the structure is separated from the ground during an earthquake, the ground is moving but the structure experienced little movement. To minimize the transmission of potentially damaging earthquake ground motions into a structure is achieved by the introduction of flexibility at the base of the structure in the horizontal direction while at the same time introducing damping elements to restrict the amplitude or extent of the motion caused by the earthquake somewhat akin to shock absorbers. In recent years this relatively new technology has emerged as a practical and economic alternative to conventional seismic strengthening. This concept has received increasing academic and professional attention and is being applied to a wide range of civil engineering structures. To date there are several hundred buildings in Japan, New Zealand, United States, India which use seismic isolation principles and technology for their seismic design.